From Washington Post. Sort of looks like it doesn't make a lot, but should be easy to double.
Ingredients
Hot water, for filling mugs
2 cups whole or reduced-fat milk (may substitute plant-based milk)
3 ounces dark chocolate chips or chopped dark chocolate
1 teaspoon vanilla extract
1 large pinch salt
2 ounces dark rum or another spirit (see NOTE)
2 ounces coffee liqueur, or another liqueur (see NOTE)
Whipped cream, marshmallows, chocolate shavings, orange zest and/or grating of nutmeg/cinnamon, for garnish (optional)
Instructions
1. Fill two mugs with hot water and set aside while you make the cocoa.
2. In a small saucepan over low heat, warm the milk, chocolate, vanilla and salt, whisking until the chocolate has melted and the mixture is smooth and uniform. Add the rum and coffee liqueur, and stir to combine. Continue to stir until the mixture is fully heated — don’t let it come to a boil.
3. Discard the hot water in the mugs, ladle the mixture into your mugs and garnish as you like.
NOTE: Other good combinations using rum: 2 ounces rum, 1 ounce coffee liqueur and 1 ounce orange liqueur; or 2 ounces rum, 1 ounce coffee liqueur and 1 ounce nut liqueur.